I have the dreaded "Jeep shakes on take off" syndrome

Hoop91 said:
Thanks Jerry. It’s a 98 TJ. Before going the SYE and CV driveshaft route, would the washer shims on t case likely improve the issue? If it is the pinion angle? Again, the fact that all issues went away with rear shaft disconnected leads me to think it’s the angle.
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The vibrations are from each u-joint at the front and rear of the rear driveshaft operating into an excessive angle... a bigger angle than the u-joints were designed for to work into.

You could temporarily try dropping the tcase skidplate another inch down to 2". Or install either a set of 1" motor mount spacers or a set of 1" taller rubber motor mount lifts.

You can't just live with this particular vibration as it will eventually start taking things out. U-joints, bearings, or seals. You have to do something soon.

I'd either bite the bullet and install a SYE & CV driveshaft or drop down to a 3" suspension lift.
 
Jerry Bransford said:
Adjusting the pinion angle should not be done with just a 2" lift. Since your control arms are stock so the pinion angle hasn't been raised, odds are good you just need to drop the t-case skidplate by about 5/8" by stacking enough washers around all six t-case skidplate mounting bolts, placed between the frame and skidplate. Due to the indentation the washers sit in, you will need more like 3/4" to 7/8" worth of washers to lower the skidplate 5/8? Just use heavy duty galvanized washers with a 1/2" bolt hole through them. Support the skidplate with a jack, loosen all 6 bolts but only remove all the bolts on one side at a time to insert the washers. That will keep the skidplate in alignment instead of slipping off to the side if all six bolts were removed at once. Dropping the skidplate 5/8" will reduce the excessive angle the rear driveshaft u-bolts are operating in that causes the vibrations.
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Jerry Bransford said:
The vibrations are from each u-joint at the front and rear of the rear driveshaft operating into an excessive angle... a bigger angle than the u-joints were designed for to work into.

You could temporarily try dropping the tcase skidplate another inch down to 2". Or install either a set of 1" motor mount spacers or a set of 1" taller rubber motor mount lifts.

You can't just live with this particular vibration as it will eventually start taking things out. U-joints, bearings, or seals. You have to do something soon.

I'd either bite the bullet and install a SYE & CV driveshaft or drop down to a 3" suspension lift.
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Got it. Based on the extreme angle causing the vibration and risk of eventually taking out parts, wouldn’t the spacer/washer approach on t case eliminate the vibration and thus = little to no risk of comprising other parts? Much appreciated Jerry!
 
x2 to the Motor mount lift, If you plan on going with a raised belly skid and or SYE/DC DS, and you are somewhat mechanically capable along with not afraid to get your hands dirty, then I would suggest it. I have a 3" Suspension lift from the previous owner and had bad vibes, I put a 1" MML and stacked some washers to help with the vibes. Putting the 1" MML helps set you up for a Tummy tuck in the long run so its worth it (at least to me)
 
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